title: Probably benign breast MRI lesions: frequency, lesion type, and rate of malignancy.
abstract: OBJECTIVE
  To determine the frequency, malignancy rate, and imaging characteristics of BI-RADS (Breast Imaging Reporting and Data System) 3 MRI detected lesions.
  
  
  METHODS
  A total of 4370 consecutive contrast-enhanced breast MRI exams from March 1, 2004, to March 1, 2009, were retrospectively reviewed. The study was HIPAA (Health Insurance Portability Accountability Act) compliant and Institutional Review Board approved. The frequency of BI-RADS 3 MRI interpretations and lesion type, as well as malignancy rate at follow-up were calculated.
  
  
  RESULTS
  There were 348/4370 (8%) BI-RADS 3 exams performed on 345 patients. There were 125 foci (35.9%), 52 non-masslike enhancements (14.9%), and 171 masses (49.1%). There were 207 lesions with biopsy or imaging follow-up of at least 24 months (mean, 32 months; range, 6-77 months) of the BI-RADS 3 lesion. Five of these 207 (2.4%) lesions were found to be malignant.
  
  
  CONCLUSIONS
  Rate of malignancy among BI-RADS 3 MRI exams with follow-up was 2.4%. Types of lesions assigned as probably benign were 35.9% foci, 14.9% non-masslike enhancements, and 49.1% masses.
authors.affiliation: Alpert Medical School of Brown University, Providence, Rhode Island.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Lourenco
authors.forename: Michelle Tsang Mui
authors.initials: MT
authors.lastname: Chung
authors.forename: Martha B
authors.initials: MB
authors.lastname: Mainiero
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000145:classification / Q000453:epidemiology* / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D015588:Observer Variation; D015995:Prevalence; D015203:Reproducibility of Results; D012237:Rhode Island / Q000453:epidemiology; D018570:Risk Assessment; D012680:Sensitivity and Specificity
keywords: MRI; breast; probably benign